U.S. patent application number 13/209668 was filed with the patent office on 2013-02-21 for brush seal with backing plate tooth.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. The applicant listed for this patent is Hemant Vinayak Gedam, Xiaoqing Zheng. Invention is credited to Hemant Vinayak Gedam, Xiaoqing Zheng.
Application Number | 20130043658 13/209668 |
Document ID | / |
Family ID | 47625366 |
Filed Date | 2013-02-21 |
United States Patent
Application |
20130043658 |
Kind Code |
A1 |
Zheng; Xiaoqing ; et
al. |
February 21, 2013 |
BRUSH SEAL WITH BACKING PLATE TOOTH
Abstract
A brush seal assembly is provided, including a sealing surface,
a side plate, a backing plate, a plurality of bristles, and a
biasing member. The backing plate is selectively located in a
stationary position and has at least one backing tooth and a
backing tip. The backing tooth has a tooth surface and the backing
tip has a tip surface. A tooth clearance is measured between the
tooth surface and the sealing surface. A tip clearance is measured
between the tip surface and the sealing surface. The tooth
clearance is less than the tip clearance. The bristles are located
between the side plate and the backing plate. The bristles include
an end portion for sealing to the sealing surface. The biasing
member exerts a biasing force upon the backing plate in a direction
towards the sealing surface. The backing tooth is configured for
selectively contacting the sealing surface.
Inventors: |
Zheng; Xiaoqing; (Niskayuna,
NY) ; Gedam; Hemant Vinayak; (Bangalore, IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Zheng; Xiaoqing
Gedam; Hemant Vinayak |
Niskayuna
Bangalore |
NY |
US
IN |
|
|
Assignee: |
GENERAL ELECTRIC COMPANY
Schenectady
NY
|
Family ID: |
47625366 |
Appl. No.: |
13/209668 |
Filed: |
August 15, 2011 |
Current U.S.
Class: |
277/355 |
Current CPC
Class: |
F02C 7/28 20130101; F05D
2240/56 20130101; F01D 11/127 20130101; F16J 15/3288 20130101 |
Class at
Publication: |
277/355 |
International
Class: |
F16J 15/44 20060101
F16J015/44 |
Claims
1. A brush seal assembly, comprising: a sealing surface; a side
plate; a backing plate selectively located in a stationary position
and having a backing tip and at least one backing tooth, the at
least one backing tooth having a tooth surface and the backing tip
having a tip surface, a tooth clearance being measured between the
tooth surface and the sealing surface and a tip clearance being
measured between the tip surface and the sealing surface, and the
tooth clearance being less than the tip clearance; a plurality of
bristles located between the side plate and the backing plate, the
plurality of bristles including an end portion for sealing to the
sealing surface; and a biasing member for exerting a biasing force
upon the backing plate in a direction towards the sealing surface,
the at least one backing tooth configured for selectively
contacting the sealing surface, wherein contact between the at
least one backing tooth and the sealing surface urges the backing
plate out of the stationary position and towards the biasing
member, and the biasing force re-positions the backing plate back
to the stationary position.
2. The brush seal assembly of claim 1, wherein backing tip is
positioned along the backing plate to provide axial support to the
plurality of bristles.
3. The brush seal assembly of claim 2, wherein the backing tip
abuts against the plurality of bristles.
4. The brush seal assembly of claim 1, wherein the brush seal
assembly is generally annular and includes a segmented
configuration where the plurality of bristles are segmented into
discrete portions around a circumference of the brush seal
assembly.
5. The brush seal assembly of claim 1, wherein a machine housing is
provided for receiving the brush seal assembly, and wherein the
machine housing includes a shoulder for engaging a corresponding
portion of the backing plate.
6. The brush seal assembly of claim 5, wherein the biasing member
is located within a recess of the machine housing.
7. The brush seal assembly of claim 1, wherein the tip clearance
ranges from about 0.3 millimeters to about 3.0 millimeters.
8. The brush seal assembly of claim 1, wherein the tooth clearance
ranges from about 0.6 millimeters to about 3.4 millimeters.
9. The brush seal assembly of claim 1, wherein the sealing surface
is an outer surface of a rotary member.
10. The brush seal assembly of claim 1, wherein the biasing member
is one of a leaf spring, a wave spring and a coil spring.
11. A brush seal assembly, comprising: a sealing surface; a side
plate; a backing plate selectively located in a stationary position
and having a backing tip and at least one backing tooth, the at
least one backing tooth having a tooth surface and the backing tip
having a tip surface, a tooth clearance being measured between the
tooth surface and the sealing surface and a tip clearance being
measured between the tip surface and the sealing surface, and the
tooth clearance being less than the tip clearance; a plurality of
bristles located between the side plate and the backing plate, the
plurality of bristles including an end portion for sealing to the
sealing surface, and the backing tip being positioned along the
backing plate to provide axial support to and abutting against the
plurality of bristles; and a biasing member for exerting a biasing
force upon the backing plate in a direction towards the sealing
surface, the at least one backing tooth being configured for
selectively contacting the sealing surface, wherein contact between
the at least one backing tooth and the sealing surface urges the
backing plate out of the stationary position and towards the
biasing member, and the biasing force re-positions the backing
plate back to the stationary position.
12. The brush seal assembly of claim 11, wherein the brush seal
assembly is generally annular and includes a segmented
configuration where the plurality of bristles are segmented into
discrete portions around a circumference of the brush seal
assembly.
13. The brush seal assembly of claim 11, wherein a machine housing
is provided for receiving the brush seal assembly, and wherein the
machine housing includes a shoulder for engaging a corresponding
portion of the backing plate.
14. The brush seal assembly of claim 13, wherein the biasing member
is located within a recess of the machine housing.
15. The brush seal assembly of claim 11, wherein the tip clearance
ranges from about 0.3 millimeters to about 3.0 millimeters.
16. The brush seal assembly of claim 11, wherein the tooth
clearance ranges from about 0.6 millimeters to about 3.4
millimeters.
17. The brush seal assembly of claim 11, wherein the biasing member
is one of a leaf spring, a wave spring and a coil spring.
18. A brush seal segment in a seal assembly, comprising: a rotary
member having a sealing surface; a side plate; a backing plate
selectively located in a stationary position and having a backing
tip and at least one backing tooth, the at least one backing tooth
having a tooth surface and the backing tip having a tip surface, a
tooth clearance being measured between the tooth surface and the
sealing surface and a tip clearance being measured between the tip
surface and the sealing surface, the tooth clearance being less
than the tip clearance; a plurality of bristles located between the
side plate and the backing plate, the plurality of bristles
including an end portion for sealing to the sealing surface, the
backing tip being positioned along the backing plate to provide
axial support to and abutting against the plurality of bristles,
the brush seal assembly being generally annular and including a
segmented configuration where the plurality of bristles are
segmented into discrete portions; a machine housing for receiving
the brush seal assembly, the machine housing including a shoulder
and a recess, the shoulder engaging a corresponding portion of the
backing plate; and a biasing member for exerting a biasing force
upon the backing plate in a direction towards the sealing surface,
the biasing member being located within the recess of the machine
housing, the at least one backing tooth being configured for
selectively contacting the sealing surface where contact between
the at least one backing tooth and the sealing surface urges the
backing plate out of the stationary position and towards the
biasing member, and the biasing force re-positions the backing
plate back to the stationary position.
19. The brush seal assembly of claim 18, wherein the tip clearance
ranges from about 0.3 millimeters to about 3.0 millimeters.
20. The brush seal assembly of claim 18, wherein the tooth
clearance ranges from about 0.6 millimeters to about 3.4
millimeters.
Description
BACKGROUND OF THE INVENTION
[0001] The subject matter disclosed herein relates to a brush seal
assembly, and more specifically to a brush seal assembly having a
backing plate including at least one backing tooth for selectively
contacting a sealing surface.
[0002] Brush seals are commonly found in a variety of applications
such as gas and steam turbines, and are typically employed to seal
a gap located between a rotary shaft and a stationary member. Brush
seals have a plurality of bristles that are sandwiched between a
forward plate and a backing plate. The bristles extend towards a
sealing surface and provide a seal between the rotary shaft and the
stationary member.
[0003] The backing plate of the brush seal provides axial support
to the bristles and also partially obstructs the gap located
between the rotary shaft and the stationary member. A clearance is
located between the backing plate and the rotary shaft in an effort
to substantially prevent the backing plate from contacting the
rotary shaft during operation. This clearance is sometimes referred
to as the fence height of the backing plate. The fence height of
the backing plate is typically more than the conventional
metal-to-metal clearance. In an effort to improve brush seal
pressure capability and reduce bristle wear, the fence height is
reduced such that the bristles have increased support and are
subjected to less bending stress from pressure loading. However,
reducing fence height may increase the risk of rubbing against the
rotary shaft during transient conditions, such as when the system
is passing resonant speeds or in the event thermal equilibrium
between components is reached. If the fence height is not adequate,
the surface of the backing plate that opposes the rotary shaft may
mushroom or smear when rubbed by the rotating surface of the rotary
shaft during transient conditions.
[0004] In the event a backing plate tip is rubbed, the edges of the
backing plate may become irregular and intermittent. This may
create a difficult situation, as the bristles may not slide easily
along on the backing plate. If the bristles are stuck on an
irregular edge of the backing plate, the bristles may become
permanently bent and worn where there are rotary shaft excursions.
Thus, the backing plate should provide axial support to the
bristles while still substantially avoiding contact with the rotary
shaft.
[0005] Several approaches currently exist for reducing or
preventing the surface of the backing plate from contacting the
rotary member while still maintaining axial support of the
bristles. For example, in one approach, the surface of the backing
plate is coated with a tribologically compatible coating or backing
layer to be more tolerant to rubbing. In another approach, a
material that facilitates rubbing between the backing plate and the
rotary surface could be employed as well to substantially avoid
mushrooming of the backing plate tip. However, these approaches may
introduce added cost and complexity to the brush seal. In another
approach, the forward plate is set to a relatively tight clearance
to serve as a bump element to protect the backing plate, but it is
typically not a viable option, because this approach will create a
jet flow that may destabilize the brush seal bristles, causing
fluttering and relatively quick wear. Therefore, it would be
desirable to provide a cost effective system for reducing contact
between the backing plate of a brush seal and a rotary shaft.
BRIEF DESCRIPTION OF THE INVENTION
[0006] According to one aspect of the invention, a brush seal
assembly is provided, including a sealing surface, a side plate, a
backing plate, a plurality of bristles, and a biasing member. The
backing plate is selectively located in a stationary position and
has at least one backing tooth and a backing tip. The backing tooth
has a tooth surface and the backing tip has a tip surface. A tooth
clearance is measured between the tooth surface and the sealing
surface. A tip clearance is measured between the tip surface and
the sealing surface. The tooth clearance is less than the tip
clearance. The bristles are located between the side plate and the
backing plate. The bristles include an end portion for sealing to
the sealing surface. The biasing member exerts a biasing force upon
the backing plate in a direction towards the sealing surface. The
backing tooth is configured for selectively contacting the sealing
surface. Contact between the backing tooth and the sealing surface
urges the backing plate out of the stationary position and towards
the biasing member. The biasing force re-positions the backing
plate back to the stationary position.
[0007] These and other advantages and features will become more
apparent from the following description taken in conjunction with
the drawings.
BRIEF DESCRIPTION OF THE DRAWING
[0008] The subject matter, which is regarded as the invention, is
particularly pointed out and distinctly claimed in the claims at
the conclusion of the specification. The foregoing and other
features, and advantages of the invention are apparent from the
following detailed description taken in conjunction with the
accompanying drawings in which:
[0009] FIG. 1 is an exemplary cross-sectioned view of a brush seal
assembly; and
[0010] FIG. 2 is a view of a portion of the brush seal assembly
illustrated in FIG. 1.
[0011] The detailed description explains embodiments of the
invention, together with advantages and features, by way of example
with reference to the drawings.
DETAILED DESCRIPTION OF THE INVENTION
[0012] FIG. 1 illustrates an exemplary brush seal assembly 10
located between a rotary member 20 and a machine housing 22. The
brush seal assembly 10 may be employed in any application requiring
sealing between two regions of varying pressure. For example, the
brush seal assembly 10 may be in employed in a gas or steam
turbine, a compressor, or a pump. The brush seal assembly 10
includes a side plate 26, a backing plate 28, a plurality of
sealing bristles 30, and a biasing member 32. The sealing bristles
30 are received between the side plate 26 and the backing plate 28.
The seal bristles 30 are typically constructed from stainless
steel, Haynes.RTM. 25 alloy, or a nickel-cobalt alloy, however it
is understood that other materials may be used as well.
[0013] The seal bristles 30 have a first end portion 40 and a
second end portion 42. The first end portion 40 is received between
two siderails 44, 46, where a first siderail 44 is attached to the
side plate 26 and the second siderail 46 is attached to the backing
plate 28. The siderails 44, 46 exert a compressive force to secure
and position the seal bristles 30 in place. In one embodiment the
siderails 44, 46 are attached to the seal bristles 30 by welding.
The second end portion 42 of the seal bristles 30 are configured to
provide sealing to a sealing surface 48 of the rotary member 20. In
one embodiment, the second end portion 42 of the seal bristles 30
may contact the sealing surface 48 as the rotary member 20
operates. The sealing bristles 30 may be angled in the direction of
rotation. Specifically, referring to FIG. 2, the seal bristles 30
are angled in a direction of rotation R of the rotary member
20.
[0014] Continuing to refer to FIG. 2, the brush seal assembly 10
includes a generally annular configuration. In one embodiment, the
brush seal assembly 10 may include a segmented design, where the
plurality of seal bristles 10 are segmented into discrete portions
or segments 50 located around the circumference of the brush seal
assembly 10. The segments 50 may facilitate assembly of the brush
seal assembly 10 between the rotary member 20 and the machine
housing 22. The brush seal assembly 10 may include any number of
brush seal bristle segments 50, such as, for example, four discrete
segments, six discrete segments, or eight discrete segments.
Referring to both of FIGS. 1-2, the biasing member 32 is located
within a recess 51 of the machine housing 22 between the brush seal
assembly 10 and the machine housing 22. The biasing member 32 is
placed between a bottom surface 53 of the recess and an upper
surface 55 of the backing plate 28. Each segmented portion 50 of
the brush seal assembly 10 may have at least one corresponding
biasing member 32. In the embodiment as shown, the biasing member
32 is a leaf spring, however it is understood that other types
biasing members may be used as well. For example, in another
embodiment the biasing member 32 could be a wave spring or a coil
spring.
[0015] Referring back to FIG. 1, the machine housing 22 includes a
hook or shoulder 54, where the shoulder 54 is used to engage with
and provide support to a corresponding portion 56 of the backing
plate 28. The backing plate 28 includes at least one backing tooth
52 and a backing tip 60. The backing tooth 52 and the tip 60 are
both protuberances that each project outwardly from an outer
surface 62 of the backing plate 28. The backing tip 60 is
positioned along the backing plate 28 to abut against and provide
axial support to the seal bristles 30. The backing tooth 52 is
positioned closer to the sealing surface 48 of the rotary member 20
than the backing tip 60. Specifically, the backing tooth 52
includes a tooth surface 66 and the backing tip 60 includes a tip
surface 68. A tooth clearance C1 is measured between the tooth
surface 66 and the sealing surface 48, and a tip clearance C2 is
measured between the tip surface 68 and the sealing surface 48. The
tooth clearance C1 is less than the tip clearance C2. In one
exemplary embodiment, the tooth clearance C1 ranges from about 0.63
millimeters (0.025 inches) to about 3.42 millimeters (0.135
inches), and the tip clearance C2 ranges from about 0.38
millimeters (0.015 inches) to about 3.05 millimeters (0.12 inches).
That is, the difference between the tooth clearance C1 and the tip
clearance C2 ranges from about 0.25 millimeters (0.010 inches) to
about 0.38 millimeters (0.015 inches).
[0016] The backing tooth 52 is configured to selectively contact
the sealing surface 48 of the rotary member 20. That is, the
backing tooth 52 is positioned such that in the event the backing
plate 28 comes within proximity of the sealing surface 48 of the
rotary member 20, only the backing tooth 52 is configured to
contact the sealing surface 48. Thus, contact between backing tip
60 and the sealing surface 48 is generally avoided. The backing
tooth 52 of the backing plate 28 typically contacts the sealing
surface 48 during a rotary member excursion, which may occur due to
thermal transient conditions, or rotor vibration when passing a
resonant speed. The functions of the backing tooth 52 are typically
two fold. First, the backing tooth 52 generally provides protection
to the backing plate tip 68 in the event of rotor excursion or
thermal pinching. The second function of the backing tooth 52 is to
act as a backup seal.
[0017] In the embodiment as shown in FIG. 1, the backing plate 28
is selectively located in a stationary position S. The backing
plate 28 remains in the stationary position S during normal
operation, until the backing tooth 52 contacts the sealing surface
48 of the rotary member 20 during thermal transient operating
conditions such as, for example, startup and shutdown. Contact
between the backing tooth 52 and the sealing surface 48 causes the
backing plate 28 to be urged out of the stationary position S, and
pushes the backing plate 28 in a first direction D1 towards the
biasing member 32. Specifically, referring to FIGS. 1-2, contact
between the backing tooth 52 and the sealing surface 48 causes the
segmented portion 50 of the brush seal assembly 10 to be urged out
of the stationary position S, and radially outwardly away from the
rotary member 20 such that the backing plate tip 60 will not
generally be rubbed by the rotary shaft 20.
[0018] The biasing member 32 exerts a biasing force F upon the
backing plate 28. The biasing force F is oriented in a direction
towards the sealing surface 48 of the rotary member 20. If the
backing tooth 52 contacts the sealing surface 48 of the rotary
member 20, the respective segmented portion 50 of the brush seal
assembly 10 is urged radially outwardly, and towards the biasing
member 32. The biasing member 32 exerts the biasing force F towards
the sealing surface 48 of the rotary member 20, which re-positions
the segment 50 back into the stationary position S.
[0019] The backing tooth 52 is employed to reduce or substantially
avoid contact between the backing tip 60 and the rotor 20, while
also reducing the tip clearance C2 between the backing tip 60 and
the sealing surface 48. Specifically, the tip clearance C2 of a
backing plate 28 employing the backing tooth 28 is generally less
than the tip clearance C2 of a backing plate 28 that does not
include the backing tooth 28. The tip clearance C2 should be
reduced to the smallest dimension possible to provide axial support
to the seal bristles, while still substantially avoiding contact
with the rotary shaft 20 through sacrificing the backing tooth 52
in a rub situation. Meanwhile the backing tooth 52 may also work as
a backup seal as well
[0020] While the invention has been described in detail in
connection with only a limited number of embodiments, it should be
readily understood that the invention is not limited to such
disclosed embodiments. Rather, the invention can be modified to
incorporate any number of variations, alterations, substitutions or
equivalent arrangements not heretofore described, but which are
commensurate with the spirit and scope of the invention.
Additionally, while various embodiments of the invention have been
described, it is to be understood that aspects of the invention may
include only some of the described embodiments. Accordingly, the
invention is not to be seen as limited by the foregoing
description, but is only limited by the scope of the appended
claims.
* * * * *